Oil burning tuyere



m L we m m .JB L w O 8 5 9 1 0 3 L w Filed Aug. 20, 1954 v INVENTORJ BY W . Assn-r W on BURNING TUYERE James S. Earle, Monterrey, Memco, assignor to American Metal filimax, lno, a corporation or New York Application August 20, 1954, Serial No. 451,134

Claims priority, application Mexico August 26, 1953 6 Claims. (Cl. 266-41) This invention relates to slag fuming furnaces and similar blowing furnaces or converters. More particularly, the invention pertains to oil burning tuyeres for such metallurgical furnaces.

Conventionally, slag fuming and like furnaces are operated with tuyeres designed to inject a suspension of pulverized coal in an air stream that enters below the surface of molten material in the furnace and undergoes combustion as it rises through the furnace. The use of coal in such furnace operation has several disadvantages, e. g.,

the costly equipment to handle, pulverize and safely store the coal. In spite of the economic and technical shortcomings of coal, no one has found, to my knowledge, a practical way of deviating from the standardized use of powdered coal by substituting the abundantly available and cheap fuel oils.

Accordingly, the principal object of this invention is the successful operation of slag fuming and like furnaces with tuyeres that are charged with a mixture of fuel oil and air.

To simplify understanding of the invention, the description will refer to the drawing which is a sectional elevation of an illustrative tuyere adapted to supply a suitable mixture of fuel oil and air to a metallurgical furnace or converter.

As shown, the tuyere body 10 is desirably a metal casting with a horizontal passage 11 and a slanted passage 12 which come together in the vicinity of threaded end 13. The angle between passages 11 and 12 may vary from about 30 to 60 degrees, an angle of approximately 45 degrees being preferred. The inlet end 14 of passage 12 is threaded so that it may be readily connected to a line supplying pressurized air. The end 15 of passage 11 which is opposite threaded end 13 is larger in diameter than the rest of passage 11 and has a slanted branch 16 of the same larger diameter as end 15. A steel ball 17 fits in end 15 and is kept from falling out by a bushing 18 which has a concave lip 19 matching the spherical contour of ball 17. Thus, the pressurized air entering tuyere body 10 through passage 12 causes ball 17 to seat tightly against lip 19 of bushing 18 and thereby form a seal to prevent the escape of air through end 15. The opening of bushing 18 is of a size to permit a poker or punch bar to pass therethrough; when a poker is introduced through bushing 18, the poker tip will displace ball 17 and force it up into branch passage 1d. When the poker is Withdrawn, ball 17 will drop down from branch passage 16 and the pressurized air will again force ball 17 to seat tightly against lip 19 of bushing 13.

An oil injector 20 is connected to the bottom of tuyere body it at a point where it will discharge oil directly into the high-velocity air stream passing therethrough. injector 2.0 is so positioned that the oil stream strikes the inside Wall of horizontal passage 11 at a point beyond the junction of slanted passage 12 with horizontal passage 11. By this arrangement, oil is prevented from being blown back through horizontal passage 11 which 2,854,229 Patented Sept. 30, 1958 would result in an oil drip and even an oil spray being discharged through bushing 18, particularly when using a poker or punch bar as above described. Injector 20 has a small opening 21 disposed at an angle to the horizontal of about 30 to 60 degrees, preferably approximately 45 degrees. instead of using injector 20 with slanted opening 21, an injector with a straight opening may be connected to tuyere body 10 at the desired angle to accomplish the same result. Threaded end 22 of injector 20 is readily connected to a supply line through which fuel oil is pumped under pressure.

Tuyere body it} is connected by its threaded end 13 to tuyere duct 23 which passes through outer wall 24 and inner wall 25 of a conventional slag fuming furnace. Thus, the oil injected angularly through opening 21 is conveyed by the high-velocity air stream from passage 12 through tuyere duct 23 into the molten material within the furnace.

In most cases, the inside diameters of passages 11, 12 and 23 will fall in the approximate range of 1 to 2 inches and frequently in the range of 1%, to 1% inches. Opening 21 of oil injector 20 has a diameter desirably,

in the range of about to inch.

In achieving successful operation of a fuming furnace for the elimination of lead and zinc from a molten metallurgical slag, I have found that the ratio of air to fuel oil must be maintained appreciably higher than is the customary practice when using powdered coal. Thus, while the air-to-coal ratio rarely exceeds cubic feet (measured at standard conditions) of air per pound of coal charged through the tuyeres, I have employed over cubic feet of air per pound of fuel oil supplied to the tuyeres. It is Well to note that the average fuel oil theoretically requires approximately 200 cubic feet of air to burn one pound of oil completely to carbon dioxide and water vapor. Actually, however, it is usual to double this theoretical quantity of air to attain satisfactory combustion of the fuel oil. As against the theoretical quantity of air, I have determined that optimum furnace operation is realized when the tuyeres convey an air-oil mixture in the range of about to 140 cubic feet of air per pound of oil which roughly corresponds to about 55 to 70% of the theoretical air requirement. Additional or secondary air is, of course, admitted to the furnace at a level above that of the tuyeres. This secondary air is in sufficient excess not only to complete the burning of the oil to carbon dioxide and water vapor but also to convert lead and zinc vapors rising from the molten slag to the corresponding oxide fumes.

In a specific example of the invention, a tuyere duct with an internal diameter of 1% inches was satisfactorily operated with a fuel oil rate of 2 to 3 pounds per minute while the air rate was varied from about to cubic feet per pound of oil. The air supplied to the tuyere was at a pressure of 5.5 pounds per square inch gage and the oil was injected into the air stream with the aid of a gear pump which developed an oil pressure at least 10 pounds per square inch higher than the pressure of the air stream.

With highly viscous fuel oils, it is advisable to preheat the oil to a temperature usually not exceeding about 80 C. to facilitate injection of the oil into the air streams in the tuyeres. Ordinary steam is adequate for such oil preheating. It is noteworthy that in accordance with this invention no particular effort is made to atomize or otherwise uniformly disperse the fuel oil in the air stream flowing through the tuyere. To the contrary, it appears advantageous to have a substantially continuous fine stream of oil conveyed with a larger stream of air directly into the molten contents of the furnace.

In the light of this disclosure, all variations conforming to the spirit of the invention are to be considered within the scope of the appended claims.

What is claimed is:

i. In the operation of the slag fuming and like furnaces involving the introduction of combustion gases into the molten masses in said furnaces, the improvement which comprises injecting fuel oil alone through small openings with a diameter not exceeding about Vs inch angularly into the'air streams flowing through the tuyeres of said furnaces, said air streams having a diameter of at least about 1 inch, proportioning said air and oil so that said air corresponds to substantially less than the quantity of air theoretically required to burn said oil completely to carbon dioxide and water vapor but not less than one-half of said theoretical quantity, and discharging said air and oil from said tuyeres into said molten masses for combustion therein.

2. The operation of claim 1 wherein the fuel oil is injected at an angle of30 to 60 degrees to the air streams flowing through the tuyeres.

Y 3, The operation of claim 1 wherein the proportioning of said air and oil is in the range of about 110 to 140 cubic feet of air per pound of oil.

4. An oil burning tuyere comprising a tuyere duct having one end discharging into'a furnace and an opposite end provided with a check valve adapted to be opened by the introduction of a poker, an air supply passage discharging angularly into said duct, and an oil injector disposed downstream relative to said air supply passage and having a small opening with a diameter not exceeding about inch positioned in the inner surface of said duct to inject oil angularly into said duct, said duct having an internal diameter of at least about 1 inch.

5. The oil burning tuyere of claim 4 wherein the air supply passage and the oil injector discharge their respective fluids at angles to the tuyere duct in the range of to degrees.

6. The oil burning tuyere of claim 4 wherein the tuyere duct has an internal diameter of 1% to 1% inches and the discharge opening of the oil injector has a diameter of at least about 5 References Cited .in the file of this patent UNITED STATES PATENTS 

